The project is oriented towards the clinical and molecular characterization of patients with Pallister-Hall syndrome and related disorders. In this protocol we perform clinical characterization including radiologic and magnetic imaging, clinical examination, interviews, behavioral and psychiatric evaluation, airway imaging, and other studies. The goal is to document the natural history and range of expressivity of PHS. In addition, we are recruiting patients who have disorders that are related to PHS, either because they are known to be allelic or they have phenotypic overlap. The molecular characterization seeks to define the range of mutations that cause PHS and related disorders. Specifically, how those mutations relate to specific phenotypic effects and to the cell biologic effects of normal and mutant GLI3.